A juicy supporting role on the show that transformed television would be the summit of most actors’ careers. For Sebastian Arcelus, it’s a jumping-off point.

Best known for the moment as Lucas Goodwin, the mostly moral sometime-boyfriend of Kate Mara’s reporter Zoe on “House of Cards,” Arcelus also has a long history on Broadway that he’s continuing this fall, even as he simultaneously films the second season of Netflix’s buzzed-about, Fincher-fueled drama.

Rehearsals for the new Broadway drama “A Time to Kill,” adapted by Rupert Holmes from the John Grisham novel, haven’t interfered with Arcelus’ job on “House of Cards,” though they have resulted in a few bleary-eyed, middle-of-the-night bus rides to and from Baltimore. “Right now I’m going back and forth, which has been sort of maddening from a scheduling standpoint,” Arcelus says. “But I’m pretty intense that way. I will stretch myself to the limit.” Despite the physical strain of the commute, Arcelus was too enthusiastic about returning to the role of Southern defense attorney Jake Brigance, one he played in a 2011 production at D.C.’s Arena Stage, to say no.

He’s also not one to waste an opportunity, a holdover from his days as a struggling, unrepresented actor who would show up at newsstands the moment Backstage hit the streets. He worked almost exclusively from casting notices he found in the pages of the magazine for three or four years before attending an open casting call for “Rent.” He sang eight bars, got cast, and was on his way to roles as a replacement in “Wicked” (where he met his wife, fellow actor Stephanie J. Block) and “Jersey Boys” before starring in the original stage production of “Elf.” “A Time to Kill” marks his first turn as a dramatic leading man. If he’s nervous about headlining a courtroom drama, he’s not saying.

“It’s exciting for me to come back and revisit this piece after having it be close to my heart,” he says, though he wasn’t originally coming to Broadway with the play, both because of presumed scheduling conflicts with “House of Cards” (the filming of which ultimately led to Arcelus missing a day or two of rehearsal) and because the economics of opening a straight play on Broadway without a massive name attached to it were daunting. And though director Ethan McSweeny rightly calls Arcelus a success story—when success is measured by consistent, quality work and not by box office grosses or tabloid mentions—Arcelus wasn’t exactly a commodity known outside Manhattan. Until “House of Cards,” that is.

“Everyone thought that, with ‘House of Cards,’ Sebastian had grown in stature to such an extent that we should have him in the part,” McSweeny says over the phone between rehearsals. “When we saw we could make it happen, it felt like the most important piece of the production fell back into place.”

With the Arena Stage run already under Arcelus’ belt, his prior knowledge of the material—which has been heavily revised since that production—eased everyone’s fears about his missing a few rehearsals to film in Baltimore. “This is not a remount,” McSweeny says. “But it certainly helped that Sebastian has more than a passing familiarity with the courtroom passages. He’s already got a great command over their arc.”

Set in the mid-’80s in the Deep South, “A Time to Kill” is as relevant today as it was when Grisham’s novel was published in 1989. Arcelus plays Jake Brigance, who is representing African-American father Carl Lee Hailey for the murder of the two white men who raped his 10-year-old daughter. What unfurls is a lot of grandstanding, a lot of politicking, and a lot of wading in murky moral waters. Brigance makes no bones about the fact that Hailey could send his legal career to the next level; the prosecuting attorney—played here by Broadway’s best interpreter of preening self-possession, Patrick Page—makes no bones about a conviction sending him to the governor’s mansion. No one’s motives are pure, and much of the drama hinges on how culpable Brigance is: In an early scene, Hailey asks if Brigance would represent him if he killed the men, and Brigance doesn’t try very hard to persuade Hailey not to do it.

“It’s an interesting question, and we’ve explored it further [than in the Arena Stage production],” Arcelus says. “Jake is not your white knight, purely altruistic, idealistic lawyer. He is complicit in a way, in that Carl Lee gives him the sense that he’s considering taking matters into his own hands. And that is fun to explore because it’s not cut-and-dried. The audience can go out and think, How would I have ruled?”

As Arcelus and McSweeny returned to the material together, neither of them shirked the work that goes into mounting a Broadway play—even one on which they had previously collaborated. “I didn’t go in thinking, This is old hat; this is gonna be great!” Arcelus says. Instead, he found himself rethinking each beat, reaffirming what it meant and why it was there. In the process, Arcelus started finding answers to questions he had left unanswered. “That has been cool,” he says. “It’s also one of those things where you’re like, ‘D’oh! How did I not figure it out then?’ I just love exploring the darker areas of his journey.”

That giddiness about the work of creating a character is typical of Arcelus, who earned a degree in political science and promptly began pursuing a career in acting. Without any practical knowledge or contacts, he opted to apply his business schooling to the process of building his résumé. Part of that plan involved writing long, personalized letters to the casting directors of regional theaters. “I didn’t just send my picture and résumé out,” he says, laughing. “I wrote life stories. It was not just ‘Can you see me for “The Pirates of Penzance”?’ It was ‘Back when I was 10 years old, I was riveted by the stories of such and such.…’ And they were honest accounts! It wasn’t like I was bullshitting. And in some cases I got an audition, and in some cases they were probably like, ‘Who the hell is this guy? This guy’s a nerd—forget him.’ ”

Let the record reflect: Arcelus was, in fact, cast in a production of “The Pirates of Penzance” based on that letter—though he ultimately did “Floyd Collins” instead.